U.S. patent number 10,955,673 [Application Number 16/318,519] was granted by the patent office on 2021-03-23 for devices for data superimposition.
This patent grant is currently assigned to Carl Zeiss Jena GmbH. The grantee listed for this patent is Carl Zeiss Jena GmbH. Invention is credited to Christoph Erler.
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United States Patent |
10,955,673 |
Erler |
March 23, 2021 |
Devices for data superimposition
Abstract
Provided are methods and devices for data superimposition, in
which an imaging device comprises a diffuser and a holographic
layer to provide a real or virtual image for an observer. In one
variant, diffuser and holographic layer are provided on different
sides of a transparent carrier. In other embodiments, the imaging
device and holographic layer are arranged in smart glasses.
Inventors: |
Erler; Christoph (Jena,
DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Carl Zeiss Jena GmbH |
Jena |
N/A |
DE |
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|
Assignee: |
Carl Zeiss Jena GmbH (Jena,
DE)
|
Family
ID: |
1000005439673 |
Appl.
No.: |
16/318,519 |
Filed: |
July 20, 2017 |
PCT
Filed: |
July 20, 2017 |
PCT No.: |
PCT/EP2017/068376 |
371(c)(1),(2),(4) Date: |
January 17, 2019 |
PCT
Pub. No.: |
WO2018/015496 |
PCT
Pub. Date: |
January 25, 2018 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20190243140 A1 |
Aug 8, 2019 |
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Foreign Application Priority Data
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Jul 21, 2016 [DE] |
|
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10 2016 113 518.6 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B
5/02 (20130101); G02B 5/0278 (20130101); G03H
1/2202 (20130101); G02B 27/0172 (20130101); G02B
27/0103 (20130101); G02B 6/0016 (20130101); G02B
5/0252 (20130101); G02B 2027/0174 (20130101); G02B
2027/0178 (20130101); G02B 2027/0112 (20130101); G03H
2225/52 (20130101); G03H 2001/2234 (20130101); G03H
2225/31 (20130101); G03H 2223/14 (20130101) |
Current International
Class: |
G02B
27/01 (20060101); F21V 8/00 (20060101); G03H
1/22 (20060101); G02B 5/02 (20060101) |
Field of
Search: |
;359/13 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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102007004444 |
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Aug 2008 |
|
DE |
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102008039737 |
|
Apr 2010 |
|
DE |
|
102011083662 |
|
Apr 2013 |
|
DE |
|
102015116408 |
|
Mar 2017 |
|
DE |
|
1798587 |
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Jun 2007 |
|
EP |
|
Primary Examiner: Alexander; William R
Attorney, Agent or Firm: Murphy, Bilak & Homiller,
PLLC
Claims
The invention claimed is:
1. An apparatus comprising: a transparent carrier arranged for a
user of the apparatus to look through; a holographic layer disposed
on the transparent carrier and sensitive to one or more certain
wavelengths of light; a spatial amplitude modulator configured to
output modulated light by modulating a source light according to
input image data, the source light being at one or more of the one
or more certain wavelengths; and a diffuser arranged to direct the
modulated light onto the holographic layer, to thereby superimpose
an image corresponding to the input image data onto a scene defined
by a field of view of the user when looking through the transparent
carrier; wherein the apparatus comprises a pair of glasses and
wherein the transparent carrier comprises at least one lens of the
pair of glasses, wherein the lenses may or may not be corrective
lenses; and wherein the pair of glasses comprise left and right
lenses having corresponding left and right side pieces for
supporting the pair of glasses on a head of the user, and wherein
the holographic layer is disposed on the front or rear surface of
the left or right lens, the diffuser is disposed on an edge surface
at a side of the same lens captured by the corresponding side
piece, and the spatial amplitude modulator and a light source
providing the source light are integrated with the corresponding
side piece.
2. The apparatus of claim 1, wherein the holographic layer is both
angle-selective and wavelength-selective, such that the holographic
layer is responsive only to light incoming at angles corresponding
to a relative positioning of the diffuser and only to light at the
one or more certain wavelengths of the source light, and is
otherwise transparent from the perspective of the user.
3. The apparatus of claim 1, wherein the holographic layer is
disposed on a front or rear surface of the at least one lens, and
wherein the diffuser is arranged on an edge surface of the at least
one lens at a relative angle to the holographic layer and
configured to redirect the modulated light according to the
relative angle.
4. The apparatus of claim 3, wherein the lenses are corrective
lenses and wherein the front or rear surface on which the
holographic layer is disposed is curved for optical correction.
5. The apparatus of claim 1, wherein the at least one lens has a
front surface facing the scene and a rear surface facing an eye of
the user, when the user uses the pair of glasses to view the scene,
and wherein the holographic layer is disposed on the front or rear
surface of the at least one lens.
6. The apparatus as claimed in claim 1, wherein the diffuser is a
holographic diffuser.
7. The apparatus as claimed in claim 1, wherein the diffuser has a
dimension of less than 1.5 cm.times.1.5 cm.
8. The apparatus as claimed in claim 1, wherein the holographic
layer is sensitive to multiple wavelengths, for superimposition of
polychromatic images.
9. The apparatus of claim 8, wherein the holographic layer
comprises multiple holographic layers, each layer sensitive to a
respective one of the multiple wavelengths and transparent to other
wavelengths.
10. An apparatus comprising: a transparent carrier arranged for a
user of the apparatus to look through; a holographic layer disposed
on the transparent carrier and sensitive to one or more certain
wavelengths of light; a spatial amplitude modulator configured to
output modulated light by modulating a source light according to
input image data, the source light being at one or more of the one
or more certain wavelengths; and a diffuser arranged to direct the
modulated light onto the holographic layer, to thereby superimpose
an image corresponding to the input image data onto a scene defined
by a field of view of the user when looking through the transparent
carrier; wherein the input image data corresponds to first and
second images to be superimposed by the holographic layer, wherein
the modulated light comprises first modulated light at one or more
certain frequencies and second modulated light at one or more other
certain frequencies, the first and second modulated light
corresponding to the first and second images, respectively, and
wherein the holographic layer is configured with wavelength
sensitivities such that it spatially positions the first image at a
first position and the second image at a second position.
11. The apparatus as claimed in claim 10, wherein the first
modulated light contains a first group of wavelengths corresponding
to first wavelength sensitivities of the holographic layer, and
wherein the second modulated light contains a second group of
wavelengths corresponding to second wavelength sensitivities of the
holographic layer.
12. The apparatus as claimed in claim 10, wherein the diffuser
comprises a first diffuser at a first diffuser position and
configured to direct the first modulated light onto the holographic
layer, and a second diffuser at a second diffuser position and
configured to direct the second modulated light onto the
holographic layer.
13. An apparatus comprising: a transparent carrier arranged for a
user of the apparatus to look through; a holographic layer disposed
on the transparent carrier and sensitive to one or more certain
wavelengths of light; a spatial amplitude modulator configured to
output modulated light by modulating a source light according to
input image data, the source light being at one or more of the one
or more certain wavelengths; and a diffuser arranged to direct the
modulated light onto the holographic layer, to thereby superimpose
an image corresponding to the input image data onto a scene defined
by a field of view of the user when looking through the transparent
carrier; wherein the transparent carrier is a lens or pane having a
front surface facing the scene and a rear surface facing an eye of
the user, when the user uses the lens or pane to view the scene,
and wherein the holographic layer is disposed on the front or rear
surface of the lens or pane; and wherein the diffuser is a
transmissive diffuser that transmissively redirects the modulated
light onto the holographic layer and wherein the apparatus further
includes an optical lens disposed between the spatial amplitude
modulator and the transmissive diffuser, the optical lens arranged
to focus the modulated light from the spatial amplitude modulator
onto a light-receiving side of the transmissive diffuser.
Description
TECHNICAL FIELD
The present application relates to devices for data
superimposition.
BACKGROUND
Devices for data superimposition are increasingly used to provide
data to a user in a simple manner. The term "data" should here by
understood in general terms. Superimposed data can comprise, for
example, images, videos, symbols, characters and/or numbers. Such
data are here preferably represented such that a user can perceive
both the data and an environment.
An area of use of such devices for data superimposition is the
automotive field, for example to provide data to a driver of a
vehicle, for example to a driver of a car, during driving. This can
be done in particular by way of corresponding elements in a
windshield of a vehicle. In this way, the driver has no need to
specially aim their gaze onto a display for example of an
instrument panel to receive data, but can perceive said data
without significantly averting their gaze from the road. Such
devices are known for example from DE 10 2008 039 737 A1.
Another area of use is what are known as smart glasses, in which
data are superimposed on a spectacle lens. With a transparent
spectacle lens, the user is then able to simultaneously perceive
the data and their environment.
The devices for data superimposition described in the present
application, however, can also be used in other applications, in
particular generally in all transparent carriers, for example
transparent panes. For example, the devices described can also be
used for transparent panes of vehicles other than cars, such as
trains, buses, ships or aircraft, but also in the property sector
for window panes. Ultimately, the devices described can be used
wherever variable contents are to be represented and/or generated.
For example, it is possible to use the devices described to make
indication elements having illumination functions, such as vehicle
tail lights, variable.
In various applications, for example in smart glasses or motorbike
helmets, where there is not much space, compact solutions in
particular are required. In addition, it is desirable to represent
images in a plurality of planes. There is additionally a
requirement in smart glasses to connect the superimposition of data
with an optical correction function of the spectacle lenses, as in
the case of conventional glasses.
SUMMARY
A device for data superimposition is provided, comprising:
a holographic layer arranged on a transparent carrier, and
an imaging device having a diffuser for generating an intermediate
image, wherein the diffuser is configured to transmit light in
accordance with data to be superimposed to the holographic layer,
wherein the holographic layer is configured to generate a real or
virtual image which is observable by a user or an image in the
plane of the holographic layer (in this case also referred to as
"image-plane hologram"), in accordance with the data to be
superimposed. It is also possible to generate a plurality of
images, with combinations of real images, virtual images and images
located in the plane of the holographic layer also being possible
here.
By using the holographic layer, the image may be generated in
particular at a desired position.
The imaging device may furthermore comprise a light source, an
amplitude modulator for modulating light from the light source in
accordance with the data to be superimposed, and an imaging optics
for imaging light from the amplitude modulator onto the
diffuser.
The diffuser may be arranged at an angle between 85.degree. and
95.degree. relative to the holographic layer.
In other embodiments, the diffuser may also be arranged at other
angles, e.g., in the angle range 95 to 0.degree., relative to the
holographic layer.
The diffuser can in particular be a holographic diffuser. In this
way, light can be directed specifically to the holographic
layer.
The holographic layer may be arranged on a first side of the
carrier, and the diffuser can be arranged on a second side of the
carrier, with the result that light passes from the diffuser
through the carrier to the holographic layer. By arranging the
diffuser and the holographic element on different sides of the
carrier, a compact construction is possible.
The light from the diffuser here passes preferably only through the
carrier to the holographic layer.
In an embodiment, the device is embodied in the form of smart
glasses, wherein the carrier is a spectacle lens of the smart
glasses, and wherein the imaging device is arranged in a side piece
of the smart glasses.
In this way, compact data superimposition onto spectacles may be
achieved. By using a holographic element, this can be combined in
particular with arched or curved panes, in particular optically
correcting spectacle lenses.
The diffuser may exhibit a dimension of less than 1.5 cm1.5 cm,
preferably less than 1.0 cm1.0 cm, which means it is able to be
accommodated easily in the side piece.
The device may be configured for representing polychromatic
images.
The image may comprise a first image at a first position and a
second image at a second position.
The holographic layer may herefor be configured to generate the
first image based on a first group of wavelengths and to generate
the second image based on a second group of wavelengths.
Alternatively, the imaging device may herefor comprise a first
imaging device and a second imaging device, with the diffuser
comprising a first diffuser of the first imaging device and a
second diffuser of the second imaging device, with the first
diffuser being arranged at a different position than the second
diffuser, with the holographic layer being configured to generate
the first image based on light from the first diffuser and to
generate the second image based on light from the second
diffuser.
With such measures, the representation in multiple image planes is
possible.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments are explained in more detail below on the basis of
embodiments. In the figures:
FIG. 1A shows a perspective view of a device for data
superimposition in accordance with an embodiment,
FIG. 1B shows a plan view of the device of FIG. 1A,
FIG. 2 shows a schematic cross-sectional view of smart glasses in
accordance with an embodiment,
FIGS. 3A and 3B show illustrations for explaining the production of
holographic elements for embodiments, and
FIG. 4 shows a schematic illustration of a device for data
superimposition in accordance with an embodiment.
DETAILED DESCRIPTION
Various embodiments are explained in detail below. These
embodiments serve merely for illustration and should not be
interpreted as limiting. In particular, a description of an
embodiment having a large number of details and features should not
be interpreted to mean that all these details and features are
necessary for implementation. Rather, some of the illustrated
features or details can also be omitted or be replaced by
alternative features or details. In addition to the explicitly
described and represented features, further features, components
etc. which are conventionally used in devices for data
superimposition can be provided.
Devices for data superimposition in the text below are understood
to mean devices that provide data to an observer, in particular
using transparent carriers to simultaneously permit a user a view
of an environment. Such devices for data superimposition can be
used in particular as head-up displays in vehicles or in smart
glasses, but are not limited hereto.
FIG. 1 shows a device for data superimposition in accordance with
an embodiment, with FIG. 1A showing a perspective view of the
device 10 and FIG. 1B showing a plan view of the device 10.
The device of FIG. 1 comprises a light source 12 for generating a
light beam. The light source 12 can be a monochromatic light
source. However, the light source 12 is preferably a multicolored
light source, for example a module having at least one red, one
green and one blue laser (RGB laser module) or a module having red,
green and blue light-emitting diodes (RGB LED module). Light from
the light source 12 is incident on a spatial amplitude modulator 13
for modulating the light spatially with respect to the intensity in
accordance with data that are to be set. An amplitude modulator 13
that can be used herefor is a micromirror arrangement (DMD,
"digital micromirror device") or a liquid-crystal arrangement
(e.g., LCoS, "liquid crystal on silicon"). In particular, the
amplitude modulator 13 in the embodiment shown is scanned using one
or more light beams from the light source 12. The amplitude
modulator 13 can be controlled by a controller (not illustrated) in
accordance with the data that are to be superimposed.
The light that is modulated spatially and temporally in this way by
the amplitude modulator 13 is imaged by an imaging optics 14 onto a
diffuser 15. An intermediate image is generated by way of the
diffuser 15. While the imaging optics 14 in FIG. 1 is schematically
illustrated in the form of a simple lens element, the imaging
optics 14 may comprise any combination of one or more lens
elements, one or more mirrors, one or more diffractive elements, or
other suitable optical elements for imaging the light from the
amplitude modulator 13 onto the diffuser 15. The arrangement of
light source 12, amplitude modulator 13, imaging optics 14 and
diffuser 15 is also referred to, within the context of the present
application, as an imaging device. The intermediate image is
generated on the diffuser 15, and the angular spectrum of light
coming from the diffuser 15 contains image information.
The diffuser 15 can in some embodiments be a simple focusing
screen. The diffuser is preferably embodied such that it has a
desired scattering characteristic such that light is transmitted in
a targeted manner in accordance with the intermediate image. In
particular, a holographic focusing screen can be used, as is
described in German patent application 10 2015 116 408.6. A
holographic focusing screen of this type can have in particular a
holographic structure which is embodied such that different
wavelengths generated by the light source 12 (e.g., a red, a green,
and a blue wavelength) are scattered at the same scattering angles.
To this end, the diffuser 15 can comprise for the different
wavelengths different holograms which are designed in each case for
the same scattering angles but different wavelengths. A diffuser of
this type can be used to avoid in particular color fringes.
In the embodiment of FIG. 1, the diffuser 15 is arranged in a first
surface of a transparent carrier 11 defined by corner points A, B,
C and D. The carrier 11 can be generated for example from a glass
or a transparent plastics material.
In the embodiment of FIG. 1, this light that is scattered by the
diffuser 15 is directed to a holographic layer 16, which is
arranged at a second side surface having the corner points C, D, E,
F of the carrier 11. The scattering characteristic of the diffuser
15 is here preferably such that as much light as possible arrives
at the holographic layer 16. Such directed scattering is possible
in particular using the abovementioned holographic focusing
screen.
The holographic layer 16 in the embodiment of FIG. 1 takes the form
of a reflection hologram and images the light from the diffuser 15,
as is shown in particular in the plan view of FIG. 1B, onto a
virtual image 18 for observation through an eye box 17 of an
observer. In other words, the observer can observe the virtual
image 18 and in this way perceive the data.
For example, the holographic layer can be implemented as a
reflection hologram for three discrete wavelengths in the red,
green and blue range according to the wavelengths of the light
source 12 so as to generate a polychromatic (i.e., multicolored)
virtual image. The distance at which the virtual image 18 is
generated from the holographic layer 16 is determined during the
manufacture of the holographic layer 16 by way of corresponding
light-exposure of a light-sensitive material. The distance can be
from a few centimeters to practically infinity. The holographic
layer 16 here has the desired optical effect for the wavelengths of
the light source 12, i.e., imaging onto the virtual image 18, while
it is transparent for other wavelengths. This permits a view
through the carrier 11. For example an embedded or laminated
holographic film having a photopolymer, in which the corresponding
holographic function was created by exposure, can be used as the
holographic layer 16. The holographic function can likewise be
integrated in a photoreactive glass or in a photorefractive glass
layer. Such a photorefractive layer can consist of a thin
photorefractive glass film, which may be applied onto a substrate.
The use of plastic, e.g., PQ-doped PMMA, is also possible.
In the embodiment shown, the surface on which the diffuser 15 is
arranged is substantially perpendicular (e.g., at an angle of
between 85 and 95.degree.) to the surface in which the holographic
layer 16 is arranged. Such a configuration resembles conventional
edge-lit holography, in which a hologram is laterally illuminated
to represent image information stored in the hologram (cf. for
example U.S. Pat. No. 5,121,229 A). By contrast, the holographic
layer 16 here serves for imaging a variable image content which is
determined by the amplitude modulator 13. In other embodiments, the
diffuser 15 can also be arranged at a different angle relative to
the holographic layer, e.g., in an angle region of 95.degree. to
0.degree.. At 0.degree., the diffuser would be located opposite the
holographic layer and parallel therewith. The position for the
diffuser would thus be on the surface ABHG rather than ABCD.
In the embodiment of FIG. 1, the diffuser is operated in
transmission, i.e., on one side it receives light from the
amplitude modulator 13 via the imaging optics 14 and, on the other
side, it emits light toward the holographic layer 16. In other
embodiments, a diffuser operating in reflection can also be used.
In this case, the diffuser is illuminated from the same side to
which it also emits the light again toward the holographic layer.
In such a case, the diffuser 15 could be arranged for example in
the surface having the corner points, E, F, G, H and receive light
from the amplitude modulator 13 via the imaging optics 14 through
the transparent carrier 11.
In the embodiment of FIG. 1, the holographic layer 16 generates a
virtual image 18. In other embodiments, the holographic layer 16
may be configured to generate a real image between the carrier 11
and the eye box 17.
In the embodiment of FIG. 1, the holographic layer 16 is
furthermore embodied in the form of a reflection hologram. In other
embodiments, a transmission hologram can be used. In this case, the
position of the eye box would be designated, e.g., 17' in FIG.
1A.
Consequently, different types of holograms and diffusers can be
used to implement devices for data superimposition according to the
invention.
FIG. 2 illustrates a cross-sectional view in plan view of a device
20 for data superimposition in accordance with a further
embodiment. The embodiment of FIG. 2 here in particular has the
form of smart glasses, having side pieces 21, spectacle lenses 22,
and a nose bridge 23.
The spectacle lenses 22 may be in particular transparent lenses to
permit a wearer of the device 20 a view of the environment. In a
preferred embodiment, the spectacle lenses 22 are curved optical
lenses that can correct defective vision of the wearer of the
device 20.
In addition, the device 20 has a device for data superimposition.
The latter will be described below for the spectacle lens 22
illustrated on the left in FIG. 2. A corresponding device can also
be provided for the other spectacle lens 22, shown on the right in
FIG. 2.
The device 20 of FIG. 2 to this end comprises an imaging device,
comprising a light source 24, an amplitude modulator 28, an imaging
optics 25, and a diffuser 25 for generating an intermediate image.
The imaging device thus formed is here dimensioned such that it can
be accommodated in the side piece 21. To this end, for example the
diffuser 26 can have dimensions of less than 1.51.5 cm, in
particular less than 1.01.0 cm. This miniaturization aside, the
function of the imaging device having the components 24, 28, 25 and
26 corresponds to the imaging device of FIG. 1 having the
components 12, 13, 14 and 15, and the details, modifications and
possible implementations that were discussed with reference to FIG.
1 for the imaging device present there are also applicable to the
imaging device of FIG. 2. For this reason, said details will not be
explained again.
Light then passes from the diffuser 26 to a holographic layer 27,
which is arranged on a side of the spectacle lens 22 that faces the
carrier (in this case the spectacle lens on the left). The diffuser
26 can in particular again be a holographic diffuser, which is
configured in a manner such that as much light as possible reaches
the holographic layer 27. A corresponding holographic layer 27 is
also arranged on the right-hand spectacle lens 22 in FIG. 2 to
receive light from a further imaging device (not illustrated),
which is arranged in the right-hand side piece 21.
The holographic layer 26 in FIG. 2 can again be designed as
described for the holographic layer 16 of FIG. 1 to generate a
virtual image for a user of the glasses. In principle, production
of a real image between glasses and eye is also possible, wherein
this image would be located in this case very close to the eye. The
holographic layer 27 in the embodiment of FIG. 2 is designed, like
in FIG. 1, in the form of a reflection hologram and the diffuser 26
in the form of a transmission diffuser. The diffuser 26 in the
embodiment of FIG. 2 is arranged approximately perpendicularly to
the holographic layer 27, for example at an angle between 85 and
95.degree.. The holographic layer 27 can here in particular also be
applied, as mentioned, onto curved spectacle lenses 22.
Holographic layers like the holographic layer 16 of FIG. 1 or the
holographic layer 27 of FIG. 2 can be generated by way of suitable
exposure of a light-sensitive material, for example the
abovementioned holographic film having photopolymer. Reproduction
is then possible also with optical contact replication.
One example of the production of a reflection hologram that can be
used for example for the holographic layer 16 of FIG. 1 or the
holographic layer 27 of FIG. 2 will now be explained with reference
to FIGS. 3A and 3B.
FIG. 3A shows an exposure of a holographic element 82 for data
superimposition, which is utilizable for example as the holographic
layer 16 of FIG. 1 or as the holographic layer 27 of FIG. 2. In
this case, for generating a holographic element 82, interference of
two spherical waves traveling in opposite directions is recorded on
the holographic element 82, in particular within a light-sensitive
holographic layer, which waves can be generated for example using a
coherent laser of adequate coherence length. A point light source
80 for emitting one of the spherical waves is situated in this case
at the later location of the diffuser 15 or 26 and emits what is
known as a reference wave, and a further point light source 81 for
emitting the other of the spherical waves is situated at the
location of the later virtual image (18 in FIG. 1B) and emits what
is known as a signal wave.
By way of the distance between the two point light sources 80, 81
from the holographic element 82, the later distance of the imaging
device from the holographic element 82 and the distance of the
later represented virtual image is determined. For example, if the
point light source 81 is situated at a distance of 8 m from the
holographic element 82, then later in the reproduction, the virtual
image will likewise be located at a distance of 8 m from the
holographic element 82.
The distance of the virtual image from the eye box (i.e.,
substantially from an eye of an observer) will later
correspondingly be at least approximately the sum of the distance
of the point light source 80 from the holographic element 82 plus
the distance of the point light source 81 from the holographic
element 82. It is possible in this way in principle to realize any
desired distance of the virtual image during later use.
FIG. 3B here shows the application of the holographic element that
is exposed as in FIG. 3A in an "ideal case." The holographic
element is illuminated, starting from a point light source 83
(corresponding to an imaging device) with reference light, which
results in the formation of a virtual image 84 (corresponding to
the position of the point light source 81 in FIG. 3A), which can be
observed by an eye (eye box) at 85.
In the real application case, rather than using the point light
source 83, an imaging device having a diffuser is used, which, in
contrast to a point light source, has an extent .DELTA.y in the
y-direction and an extent .DELTA.x in the x-direction. This can
result in distortions as compared to the ideal case of FIG. 3B, but
for practical applications these are to a certain degree
negligible, depending on a desired image quality. With preference,
the extent of the diffuser is selected to be relatively small, and
the diffuser is arranged near the location of the point light
source 80.
For a plurality of colors, it is then possible to stack a plurality
of holographic elements 82 one above the other for forming the
holographic layer 16 of FIG. 1A or 27 of FIG. 2, one layer for each
desired wavelength. As already mentioned, the holograms are both
wavelength-selective and angle-selective, which means that they are
transparent in particular for wavelengths other than the operating
wavelengths of light source 12 or 24.
The wavelength-selectivity and angle-selectivity can also be used
to represent contents in a plurality of planes. This will be
explained below.
In this case, image representation (virtual and/or real) can be
effected, as mentioned, in a plurality of planes, at different
angles, and/or generally at different locations. This process takes
advantage of the fact that the holographic layers used, in
particular volume holograms, operate, as already described, both
wavelength-selectively and angle-selectively. Consequently,
different colors can be imaged at different locations and/or be
observed from different angles by selecting for example the
directions and shapes of reference beam and signal beam to be
different for different wavelengths when generating the holographic
element.
In particular, color images (real or virtual) can be generated at
different locations by way of red, green and blue wavelengths,
which differ in terms of wavelength by more than a sensitivity
region of the respectively used hologram. For example, the
operating wavelengths 532 nm (green), 460 nm (blue) and 660 nm
(red) can be used for a first image, while the operating
wavelengths 520 nm (green), 442 nm (blue) and 647 nm (red) can be
used for a second image. By combining corresponding volume
holograms, it is possible hereby to generate for example a first
virtual image at a first distance from the holographic element, for
example 1 m, and to generate a second image at a second distance,
for example 1.5 m, with a polychromatic representation, including
white, being possible for each of said images. Similar can also be
implemented for monochromatic images with in each case only one
wavelength. The image generation can be realized with one imaging
device, which then generates 6 different colors overall, or
alternatively with separate imaging devices, which can also be
arranged at different angles. An observer located in the eye box
then sees both contents at different distances. In this case, each
holographic element only sees "its" operating wavelengths and is
otherwise transparent. Combinations with even more wavelengths and
different distances are also possible.
In embodiments in which the imaging devices are located at
different locations, it is also possible to use the same
wavelengths for both images, because, as mentioned, the holographic
elements are also angle-selective. A corresponding embodiment is
illustrated in FIG. 4. In the embodiment of FIG. 4, a holographic
element 122 contains volume holograms for two different imaging
devices, of which diffusers 120, 121 are illustrated. Based on
light from the diffuser 120, a virtual image at a location 123 is
generated, and, based on light from the diffuser 121, a virtual
image at a location 124 is generated, the latter having a distance
from the holographic element 122 which differs from that of the
location 123. The two virtual images can then be observed within an
eye box 125. The production of the volume holograms by exposure for
the two imaging devices 120, 121 can be effected in separate layers
and in each case as discussed above.
In the example illustrated in FIG. 4, the virtual images at the
locations 123, 124 can be viewed from the same eye box 125, that is
to say viewed simultaneously. However, other variations are also
possible. For example, the holographic element 122 and the
diffusers 120 and 121 may be configured such that the virtual
images can be observed "one next to the other," as it were, which
can effectively increase the size of the eye box. The refinement
may also provide, e.g., when using the embodiment of FIG. 1 in a
vehicle, that separate images can be observed from different
positions, for example from a driver position and a passenger
position in a vehicle. In this way, different contents can be
represented for different persons. Overall, it is thus possible to
provide different virtual or real images using one or more imaging
devices, possibly using different operating wavelengths, at
different locations and/or for observation from different
locations.
In other embodiments, three-dimensional contents (3D contents) can
also be represented.
In some embodiments, similar as stated above, separate virtual or
real images are generated to this end for a left and a right eye in
correspondingly small eye boxes. If the images are correspondingly
selected with different perspectives, a stereo effect can be
generated hereby. This is possible in particular in smart glasses
like the embodiment of FIG. 2.
In this way, the properties of holographic elements can be used to
create a spatial impression. This offers freedoms with respect to
the contents represented.
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